<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <title>原生js 当前时间 倒计时代码</title>
  <style>
  *{margin:0;padding:0;}
  body{text-align:center;}
  .text{margin-top:150px;font-size:14px;}
  </style>
  <script>
    window.onload=function(){      
      getMyTime(); 
      getMyTime1();  
    }
    //1.前面补0
    function p(n){
      return n<10?'0'+n:n;
    }
    //2.倒计时
    function getMyTime(){      
      var startDate=new Date();
      var endDate=new Date('2017/9/8 11:15:00');
      var countDown=(endDate.getTime()-startDate.getTime())/1000;
      var day=parseInt(countDown/(24*60*60));
      var h=parseInt(countDown/(60*60)%24);
      var m=parseInt(countDown/60%60);
      var s=parseInt(countDown%60);        
      document.getElementById('time').innerHTML=day+'天'+p(h)+'时'+p(m)+'分'+p(s)+'秒';
      setTimeout('getMyTime()',500);
      if(countDown<=0){
       document.getElementById('time').innerHTML='活动结束'; 
      }       
    }
    //3.当前时间
    function getMyTime1(){
      var myDate=new Date();
      var year=myDate.getFullYear();
      var month=myDate.getMonth()+1;
      var day=myDate.getDate();
      var week=myDate.getDay();
      var array=['星期日','星期一','星期二','星期三','星期四','星期五','星期六',];
      var hour=myDate.getHours();
      var minute=myDate.getMinutes();
      var second=myDate.getSeconds();
      document.getElementById('time1').innerHTML=year+'年'+month+'月'+day+'日'+' '+array[week]+' '+p(hour)+':'+p(minute)+':'+p(second);
      setTimeout('getMyTime1()',500);
    }
  </script>
</head>
<body>
  <div class="text">
    <p>倒计时间：<span id="time"></span></p>
    <p>当前时间：<span id="time1"></span></p> 
  </div>
</body>
</html>